There are some very experienced RV outfitters in the Eugene Oregon area.
Oregon Motorcoach does interior modifications and is a quality vendor IMHO.
Carrier & Sons has a good reputation also and is nearly next door.
Do some web surfing and then credential checking.
Or......do as many of us have done. DIY.
My front LED TV (replacing a tube type) was installed by me for a cost of about $35. There are lots of pictures and threads on the Web to pattern after.
Monoprice.com has mounts and a few sticks of wood plus your new TV may be all that is needed.